The purpose of this research proposal is to contribute, at the molecular level, to a better understanding of the mechanisms responsible for viral specific DNA synthesis in Herpes simplex virus I infected cells. The objective of this proposal is to locate the origin of viral specific DNA synthesis in infected cells. The unique aspects of this proposal are (1) to examine the DNA products made after release of viral DNA synthesis from drug inhibition to locate the origin of initial rounds of synthesis, and (2) to apply a modification of the restriction endonuclease analysis of replicating DNA as described by Danna and Nathans (20) to locate the origins of the later rounds of synthesis. In addition, to fulfill these goals it will be necessary to map regions "suspected" of containing the origin with restriction endonucleases and electron microscopy, and thereby provide for its detailed localization. The fulfillment of the specific aims of this applications are crucial for further molecular investigations that test the relationship between the regulation of viral DNA synthesis and the suspected etiologic role of Herpesvirus in human cancer.